1. Field of the Invention
The present invention relates to the assembly and adjustment of an optical kernel device suited for liquid crystal display (LCD) projectors.
2. Description of the Prior Art
Liquid Crystal Display (LCD) projectors are generally classified into two types, one type being a transmission-type LCD in which a desired display is achieved by observing, from a side of the facing substrate, light incident on the liquid crystal from a side of the TFT substrate, and the other type being a reflective-type LCD such as a liquid crystal-on-silicon (LCoS) projector in which a desired display is achieved by having light incident on the liquid crystal from the side of the facing substrate reflect on the side of the reflective substrate and by causing the light to be emitted from the side of the facing substrate.
When assembling optical elements, center of the optical axis and focusing or imaging position of the optical kernel device must be carefully adjusted. In some applications, the installation frames of the optical devices are designed as adjustable machinery. In some other applications, the adjustment (known as “POP” adjustment) or alignment of the optical kernel device is done by a pin-to-hole method.
FIGS. 1-5 illustrates the assembling process and the pin-to-hole adjustment method of a three-panel optical kernel assembly according to the prior art, wherein FIG. 1 is an exploded perspective view of parts of an optical kernel assembly 10; FIG. 2 is a perspective view of an optical kernel assembly 10 before the installation of the liquid crystal panel; FIG. 3 is a perspective view of an optical kernel assembly after the installation of the liquid crystal panel; FIG. 4 is a perspective view of an optical kernel assembly after pin-to-hole adjustment; and FIG. 5 is a perspective view of an optical kernel assembly after adhesive strip sealing.
As shown in FIG. 1, optical kernel assembly 10 comprises a base frame 20, a top frame 30, a polarizing beam splitter (PBS) 40 mounted between the base frame 20 and the top frame 30, triangle frame 50, upper positioning piece 60, lower positioning piece 70, liquid crystal panel 80, and snap fastener 90. The base frame 20 further comprises a front bracket portion 22 for installation of a projection lens (not shown). The PBS 40 is mounted on a center position of a rear stage 24 of the base frame 20. 45-degree projections 25 are provided on the rear stage 24.
Typically, triangular venting holes 26 for heat dissipation are disposed next to the 45-degree projections 25. The top frame 30 has similar triangular venting holes 36 corresponding to the triangular venting holes 26. Further, along one side of each triangular venting hole 36, a slot 34 is provided, thereby forming a rib 38 between the slot 37 and each triangular venting hole 36.
The triangle frame 50 has three vertical faces and two horizontal faces. Initially, two optical glass plates 54 are mounted on two faces of the three vertical faces, temporally leaving one face thereof open. The open face of the triangle frame 50 will be covered with the liquid crystal panel 80 in a later stage. The upper horizontal face of the triangle frame 50 has a recess 52 such that a slim protrusion 58 is formed on the upper horizontal face of the triangle frame 50.
The upper positioning piece 60 comprises two positioning pins 62. The upper positioning piece 60 further has a bent portion 61 on which two screw apertures 64 are provided. The lower positioning piece 70 comprises two positioning pins 72 and two screw apertures 74. The liquid crystal panel 80 has corner holes 82 corresponding to the positioning pins 62 and 72.
As shown in FIG. 2, the triangle frame 50 is mounted between the top frame 30 and the base frame 20. The triangle frame 50 leans against the 45-degree projection 25 at its bottom and is fixed by the snap fastener 90 through the venting hole 36 and the slot 37. The snap fastener 90 clamps the rib 38 of the top frame 30 and the slim protrusion 58 of the triangle frame 50 together. After installing the triangle frame 50, the upper positioning piece 60 and the lower positioning piece 70 are screwed onto the top frame 30 and the base frame 20, respectively, by screws.
As shown in FIG. 3, the liquid crystal panel 80 is then mounted onto the optical kernel with the pins 62 and 72, and the other two panels (not shown) are subsequently mounted onto the optical kernel with respect to the other two faces of the PBS in the same manner. After the three panels are mounted, a modulation step is performed to stack color images of the three panels and focus the images on the lens. Ordinarily, a six-axis adjustment jig is adopted to assist on the modulation step.
As shown in FIG. 4, after the three color images emitted from the respective three panels are stacked, the three panels are fixed on the optical kernel using ultra violet seal or weld 120.
Finally, as shown in FIG. 5, the inner space of the triangle frame 50 and the panel peripheral are sealed with an adhesive strip 130 in order to prevent dust or particles from entering the triangle frame 50. The above-described prior art is disadvantageous because when the ultra violet seal shrinks or other parts shrink or expand with the temperature, multidirectional cumulative tolerance occurs in the conventional assembly and leads to image misalignment.
In addition, it requires much time to adjust three panels so as to stack three images and may lag the fabrication. Furthermore, the above-described prior art is not reliable because particles or dust are often introduced during the assembly process before sealing the panel peripheral.
Further, the prior art pin-to-hole method needs snap fasteners to manually fix the triangle frame before the assembly of the liquid crystal panel, leading to extra cost and time.